1. Field of the Invention
The present invention relates to an image display device, and more particularly to an image display device using a liquid crystal.
2. Description of the Related Art
An image display device using a liquid crystal comprises a plurality of switching elements arranged in a matrix form on a substrate, transparent pixel electrodes connected to the respective switching elements, and a transparent common electrode provided opposite to the transparent pixel electrodes. The liquid crystal is sandwiched between the transparent pixel electrodes and the transparent common electrode. A voltage is applied between a selected one of the transparent electrodes and the transparent common electrode to control the polarizing characteristic of the liquid crystal at the selected pixel or to adjust the amount of light transmitted through the liquid crystal, thereby displaying a desired image.
FIG. 15 shows the conventional structure of a pixel portion having a switching action. In the figure, reference numeral 101 designates a quartz substrate, numeral 102 a polycrystalline silicon (hereinafter referred to simply as poly-Si) thin film for forming a switching TFT (thin film transistor), numeral 103 a gate oxide film, numeral 104 a poly-Si thin film for a gate electrode, numeral 105 n-type regions by which a source and a drain of the TFT are provided, numeral 106 an NSG (nondoped-silicate-glass) film, numeral 107 an A1 line film for wiring, numeral 108 a silicon nitride film, numeral 109 a Cr film for ITO (indium tin oxide) contact, numeral 110 an ITO film as a transparent pixel electrode, numeral 111 an NSG film for passivation, and numeral 112 an A1 electrode for ITO contact.
In the above-mentioned structure of the pixel portion, since the Cr film 109 for protection of the A1 electrode film 112 must be formed in order to prevent the A1 film 112 from being corroded by an etching solution which is used for patterning the ITO film 110 to form the transparent pixel electrode, a process for fabrication of the device becomes complicated. Further, breakages may be generated in the silicon nitride film 108 and/or the NSG film 106 in the course of the process steps of forming the Cr film and the ITO film so that breakdown of the A1 line film 107 occurs, thereby deteriorating the fabrication yield.